Congress put aside intense political differences over Iranian nuclear talks on Tuesday and agreed on a mechanism to review the historic deal without imposing restrictions that could have sunk negotiations entirely.

In a rare outbreak of bipartisan compromise and a partial victory for the White House, the Senate foreign relations committee voted unanimously to amend language in legislation that once threatened to give congressional hawks a chance to derail nuclear diplomacy and risk resorting to military strikes.

Instead, just six weeks after a passionate address to Congress by Israeli prime minister Binyamin Netanyahu urging full-throated opposition to the process, the revised language paves the way for US lawmakers to vote on the final nuclear deal with few strings attached.

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Crucially, the language no longer insists that the White House certify that Iran has fully renounced terrorism, something the administration felt was an impractical obstacle designed to scupper the talks.

Moderate Republicans on the foreign relations committee described the new bill as a compromise designed to ensure they had some say over the final deal rather than no say at all.

“I think we have reached a balance here,” said committee chairman Bob Corker, claiming the bill showed the “re-emergence of the foreign relations committee becoming more than just a debating society”.

But the concessions were sufficient to bring even the most liberal Democrats on board and were cautiously welcomed by the White House, which had originally opposed giving Congress such a say in the process.

“This bill has been changed from a point where I could not support it to a point where I can,” said Democrat Barbara Boxer. “I feel good that we have moved to a place that does not threaten these ongoing negotiations.”

“There is no such thing as perfection,” she told Corker and ranking Democrat Ben Cardin. “But I think you two have struck just the right balance.”

A crucial change in the balance of power on the committee came with the removal of hawkish Democrat Bob Menendez, who stood aside as a ranking member after the Department of Justice indicted him on corruption charges on 1 April.

Conservative Republicans staged a brief attempt to upend the new compromise by seeking an amendment reinstating the requirement that Iran certify it does not support terrorism, but that measure was defeated by 13 votes to 6.

“I am not just concerned about destroying the delicate balance of this bill; I am concerned about the destruction of Israel,” said Rubio.

But all 19 senators on the committee voted for the overall revisions, which include reducing the review period to 30 days, and sent the watered down bill to the full Senate.

Earlier, the White House indicated it was likely to drop its threat to veto the bill so long as senators stuck to the new language.

“If presented with a compromise along the lines that I just laid out here, that would be the kind of compromise the president would be willing to sign,” said Obama spokesman Josh Earnest.

“It would not be an up or down vote on the deal ... However, as we’ve also long insisted, [that] does not mean there is not an important role for Congress to play.”

Republicans pushed back, insisting the White House had moved from its original position of consulting Congress.

“In spite of what might be being said by buildings at the other end of Pennsylvania Avenue, this legislation is exactly what we have been working on since day one ... with 100% of the integrity,” said Corker.

But others were in a glum mood on Tuesday, and the legislation fight may move instead to the House of Representatives, where there is still substantial opposition but fewer chances to block the White House without Senate support.

“I would rather have a role than no role whatsoever,” said Republican senator Ron Johnson.

“This bill turns advise and consent on its head by allowing a vote of disapproval. It is an incredibly limited role; it is a role with very little teeth.”

Many obstacles to the talks also remain overseas.

Iran’s foreign minister, Mohammad Javad Zarif, said negotiations on the nuclear deal would resume on 21 April, involving senior diplomats and experts who would work on a text of a final comprehensive agreement due to be completed by the end of June.

“That’s a difficult exercise, particularly with all the lawyers involved in the process and looking at the nitty-gritty of every word that is written down,” Zarif told journalists during a visit to Madrid.

Both Iran’s supreme leader, Ali Khamenei, and President Hassan Rouhani have said sanctions should be lifted immediately once the agreement comes into force, while western officials have said that Iran would have to take significant steps to dismantle its existing nuclear infrastructure first.

Meanwhile, Russia showed signs of breaking ranks with the other five world powers involved in the nuclear negotiations, with the announcement that it would go ahead with the delivery of sophisticated air-defence missiles – the S-300 system, which Moscow has withheld since 2010, at the request of its western negotiating partners.

Explaining the decision, the Russian foreign minister, Sergei Lavrov, said: “We are convinced that at this stage this kind of embargo, especially a separate Russian free-will embargo, is completely irrelevant.”

He argued the missiles were “a completely defensive weapon” that would “not adapted for aggression and will not endanger the security of any state in the region, certainly including Israel”.

The White House expressed its concern about the prospective missile sale, estimated to be worth $800m to Russia, and US secretary of state John Kerry raised the issue directly with Lavrov.

Russia also said it has struck a barter deal with Iran, exchanging Iran oil for Russian grain and other commodities, although traders said they saw no sign of any increased shipments of either.

German chancellor Angela Merkel urged the international community to maintain a united approach to sanctions, arguing that there was still work to do before an agreement could be finalised.

“This is not a new issue. It has come up before, and we had expressed our concerns in the past,” said Catherine Ray, a spokeswoman for the EU. “We continue to be concerned, but we believe it does not affect the ongoing negotiations.”

Experts said that as the missiles were part of a defensive system, their export to Iran should not represent a violation of the UN arms embargo on the country.